1. Field of the Invention
The present invention relates to a measurement method for measuring a position of a tool center point of a robot and a measuring apparatus for implementing such method.
2. Description of the Related Art
When using an industrial robot, a position of a tool center point (TCP) with respect to a tool attachment surface of the robot is measured. The measurement of the tool center point is a fundamental and important operation and it is performed mainly by one of two ways.
In Japanese unexamined patent publication No. H08-8.5083, an operator positions a tool center point attached to a tip of a robot at a particular point in a space with a plurality of tool orientations to calculate the position of the tool center point by using a plurality of positioning positions. In this case, the position of the tool center point can be calculated without special jigs and the like. However, in Japanese unexamined patent publication No. H08-85083, setting accuracy of the tool center point and time required for the setting operation depend on the operator's skill and the setting accuracy and time are not always stable.
Japanese Patent No. 4191080 discloses a method for automatically measuring a position of a tool center point by using an imaging device, for example, a camera. In this case, stable setting accuracy and time can be obtained without dependence on the operator's skill. Furthermore, in Japanese Patents No. 4021413 and No. 3394322, as well as in Roger Y. Tsai, “An efficient and accurate camera calibration technique for 3d machine vision”, Proc. Computer Vision and Pattern Recognition '86, pp. 364-374; 1986, measurement techniques using the robot and camera are disclosed.
However, in Japanese Patent No. 4191080, an imaging device, such as a camera is needed. Further, in Japanese Patent No. 4191080, when it is difficult to measure the setting point of the tool center point by using the imaging device, a special jig for substituting for the tool center point is needed. Moreover, when such a special jig is used, any positional error between the measurement point on the special jig and the actual, setting position of the tool center point will reduce the setting accuracy of the tool center point.
The present invention has been made in view of the above circumstances and has an object to provide a measurement method that can stably measure a position of a tool center point with respect to a tool attachment surface with high accuracy in a short time without using a special jig substituting for the tool center point, and a measurement apparatus for implementing such method.